Date: Thu, 11 Nov 2021 07:45:51 +0000 From: HAGIO KAZUHITO(?????) <k-hagio-ab(a)nec.com&gt; To: Philipp Rudo <prudo(a)redhat.com&gt; Cc: "Discussion list for crash utility usage, maintenance and development" <crash-utility(a)redhat.com&gt; Subject: Re: [Crash-utility] [PATCH] Fix live debugging with lockdown=integrity Message-ID: < TYYPR01MB67772F7C8616E337FF66787CDD949(a)TYYPR01MB6777.jpnprd01.prod.outlook.com > Content-Type: text/plain; charset="iso-2022-jp" -----Original Message----- > With kernel lockdown the access to kernel interfaces that allow to > extract confidential information (lockdown=confidentiality) or modify a > running kernel (lockdown=integrity) can be restricted. Two of the > interfaces that can be restricted are /dev/mem (integrity & > confidentiality) and /proc/kcore (confidentiality). With > lockdown=integrity this leads to a situation where /dev/mem exists but > is not readable while /proc/kcore exists and is readable. This breaks > crash's live debugging when it is invoked without argument, i.e. > > $ crash > [...] > crash: /dev/mem: Operation not permitted > > while passing /proc/kcore as image succeeds. The reason for this is that > crash always picks /dev/mem as source when it exits but doesn't check if > it is readable. Fix this by only selecting /dev/mem when it is readable. > > Signed-off-by: Philipp Rudo <prudo(a)redhat.com&gt; Thank you for the patch. Acked-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; Kazu > --- > filesys.c | 2 +- > main.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/filesys.c b/filesys.c > index 3361b6c..43cbe82 100644 > --- a/filesys.c > +++ b/filesys.c > @@ -3666,7 +3666,7 @@ get_live_memory_source(void) > if (pc->live_memsrc) > goto live_report; > > - if (file_exists("/dev/mem", NULL)) > + if (file_readable("/dev/mem")) > pc->live_memsrc = "/dev/mem"; > else if (file_exists("/proc/kcore", NULL)) { > pc->flags &= ~DEVMEM; > diff --git a/main.c b/main.c > index 71c59d2..b278c22 100644 > --- a/main.c > +++ b/main.c > @@ -1119,7 +1119,7 @@ setup_environment(int argc, char **argv) > pc->flags2 |= REDZONE; > pc->confd = -2; > pc->machine_type = MACHINE_TYPE; > - if (file_exists("/dev/mem", NULL)) { /* defaults until argv[] is parsed */ > + if (file_readable("/dev/mem")) { /* defaults until argv[] is parsed */ > pc->readmem = read_dev_mem; > pc->writemem = write_dev_mem; > } else if (file_exists("/proc/kcore", NULL)) { > -- > 2.31.1